1. Technical Field
The present invention relates to an entry detection device, a robot, and an entry detection method.
2. Related Art
According to the related art, a technique of detecting an entry of a person into a danger zone or an entry of a suspicious person into private land using a camera is known. For example, JP-A-2010-231713 discloses a technique in which whether an optical path from a light source or a reflection mirror arranged along a predetermined boundary to a camera is intercepted or not is determined based on an output from the camera, thus detecting an entry of a person into a danger zone beyond the boundary. JP-A-2010-15258 discloses a technique in which each of light emission patterns of plural light sources is provided with certain information, thus specifying which of the optical paths from the light sources to the camera a trespasser is in. In these techniques, it is determined that there is an entry when a lighting pattern of a light source and a luminance pattern in a specified area detected by a light sensor do not coincide with each other.
However, with the related-art techniques, when a light source is off, an entry across the optical path from that light source to the camera cannot be detected. Meanwhile, if the light source is constantly on, a person can easily make an entry by installing a dummy light source in the optical path. Therefore, it is not desirable to keep the light source on constantly.
Also, in the related-art techniques, since a time-series light emission pattern in which the light source is turned on and off and a time-series luminance pattern in a specific area detected by the light sensor are compared to detect an entry, the entry cannot be detected based on each frame of a digital image outputted from the camera. Therefore, there is a problem that there is a delay between the occurrence of the entry and the detection of the entry.